Belgian scientists use new technology in search for elementary particles

Sterile neutrinos; the next ‘big’ thing

Elementary particles, and the quest to discover them, have never been hotter. The Higgs boson became a global sensation, and the men who predicted its existence won the Nobel Prize. Now Belgian scientists are turning their attention to the next big thing: sterile neutrinos. With the help of French and British colleagues, they are using a revolutionary technology to record evidence that these particles exist.

A European consortium of two French, two British and three Flemish universities and one federal research institute (UAntwerp, UGent, VUB and SCK•CEN in Mol) joined forces in early 2013. Together, they have developed a ‘neutrino experiment’. The project is named SOLID, which stands for Search for Oscillations with a Lithium6 Detector (see pictures).

The scientists want to record sterile neutrinos. “These elementary particles may be linked to the particle for which Belgian François Englert and Briton Peter Higgs were awarded the Nobel Prize for physics in 2013,” says Prof Nick van Remortel (UAntwerp). “If these new elementary particles are actually found, it will immediately answer many fundamental questions about the origin of mass and the stability of the universe.”

Very weak interaction

There is no doubt that neutrinos exist. These elementary particles were first discovered in the 1950s at a US nuclear reactor at Savannah River, South Carolina. They are also produced in vast quantities inside the sun. They are very difficult to record, however, because they barely interact with matter. Every second, about 50 billion neutrinos pass through every square centimetre of our bodies without us ever noticing.

By 2016, scientists hope to build a neutrino detector, weighing over two tonnes, which will be used to look for these sterile neutrinos over a period of three years. The scientists, including several Oxford researchers, are using a new type of particle detector: one that is extremely sensitive to neutrinos. Van Remortel: “This absolutely revolutionary technology could even be used for the remote detection of nuclear activity worldwide — a very interesting way of verifying compliance with non-proliferation agreements.”

International race

The particle detector will be built near the BR2 research reactor at SCK•CEN in Mol, Belgium. This reactor, which is responsible for a large proportion of the global production of medical radioisotopes used for imaging and cancer therapy, also appears to be ideal for carrying out fundamental research in the field of elementary particles.

"We are proud to be able to use our expertise and our BR2 facility — unique in this respect — to contribute to the success of this very exciting project", says Prof Eric van Walle, Director-General of SCK•CEN. “This search for sterile neutrinos shows that our institution can offer very interesting prospects for developing and expanding this type of fundamental research.”

The experiment has been made possible partly thanks to financial support from the Fund for Scientific Research Flanders, the Hercules Foundation and Belspo. Van Remortel: “This project demonstrates that research centres such as SCK•CEN have top-level research facilities and technical expertise, allowing them to compete with the world’s major research institutions. This means we are well equipped for this race, because other consortiums around the world are also looking for sterile neutrinos.”

Sterile neutrinos

A neutrino is an elementary particle with no electric charge, produced in high-energy collisions between nucleons. Scientists suspect that neutrinos have almost no mass. Only very rarely do they collide with matter; most of the time, they simply pass right through it. Detecting ordinary neutrinos is hard enough as it is, but sterile neutrinos are even more elusive. Particle physicists believe that they may even be able to solve the mystery surrounding dark matter if they manage to observe sterile neutrinos.